Explanation: Iapetus, Saturn's
third largest moon, is a candidate for
the strangest moon of Saturn.
Tidally locked
in its orbit around the ringed gas giant,
Iapetus is sometimes called
the yin-yang moonbecause
its leading hemisphere is very dark,
reflecting about 5 percent of the Sun's light,
while its trailing hemisphere is almost as bright as snow.
This recent Cassini spacecraft
flyby
image is one of the closest
views ever.
It spans about 35 kilometers across a cratered
transition
zone between bright and dark terrain.
Iapetus itself has a density close to that of water ice, but
the detailed reflective properties of the
dark material suggest an organic composition.
Honoring the moon's discoverer, the dark terrain is called
Cassini Regio.